1. Field of the Invention
The present invention relates to a synthetic resin made chamber of a conduit system for an internal combustion engine and more particularly to a noise insulation structure of the synthetic resin made chamber including an intake manifold and an intake chamber.
2. Discussion of Prior Art
In recent years, intake manifolds made of synthetic resin attract an interest in view of weight reduction, cost reduction and recycleability of automobile components. However, synthetic resin intake manifolds have a defect that noise is penetrable because of light weight. In order to effectively insulate and eliminate a noise propagated from air stream in the intake manifold (hereinafter, referred to as intake noise), the synthetic resin intake manifolds are inferior to aluminum alloy made intake manifolds.
The synthetic resin intake manifold with a larger wall thickness has a greater effect of noise insulation but has a disadvantage in productivity due to more elongated time for curing resin, therefore there is a limit in increasing the wall thickness of the synthetic resin intake manifold.
This problem is not limited to synthetic resin intake manifolds and also occurs in fabricating miscellaneous synthetic resin chambers including synthetic resin intake chambers.
It is an object of the present invention to provide a synthetic resin chamber having a high noise insulation ability and capable of being manufactured at low cost.
In order to achieve the object, a noise insulation structure of a conduit system of an internal combustion engine comprises a synthetic resin made chamber and a noise insulation member installed on the chamber in such a manner as covering the chamber. Specifically, the synthetic resin made chamber has a plurality of ribs and a plurality of first grooves formed between two adjacent ribs on the outer surface thereof, the noise insulation member has a plurality of projections extending along the ribs and a plurality of second grooves formed between two adjacent projections, the ribs fit to the second grooves and the projections fit to the first grooves so that the chamber has a close contact with the noise insulation member.
Further, the projection has a plurality of cylindrical blind-end bores provided along an extending direction of the projection on a top portion of the projection. These cylindrical blind-end bores make air columns when the chamber is covered with the noise insulation member and the air columns serves as muffling noise due to the resonance effect.